Microseismic and Vibroseismic Testing of a House: Comparative Study of Results with the Example of a Typical Privately Owned Residential House in Bishkek, Kyrgyzstan

Аннотация

By virtue of their cost-effectiveness and ease of implementation in various practical situations, microseism-analysis methods are most widely used in seismic engineering surveys. It has been shown that analyzing the response of a structure to microseisms usually yields fairly complete information on its resonance properties and spectral ratio. An inherent disadvantage of impacting a structure with a field of microseisms is that seismic vibrations thus produced have small amplitudes, which in principle prevent detection of probable nonlinear responses from both the structure and soil strata to large earthquakes. To a certain extent, especially for small-sized structures, this disadvantage can be compensated by using the technique of artificial vibration impacts. The paper compares the results of applying microseism-analysis methods and the technique of artificial vibration impacts for seismic engineering survey of a typical small residential house. A vibratory roller is used as a source of impacts. This vibroroller enables simulation of impacts with an intensity of up to VI on the entire surveyed house and up to IX on some of its components. The two approaches have produced results that agree well in terms of the estimated characteristics of the structure. However, when studying soil strata with vibration impacts, an additional low-frequency diffuse maximum was observed with a period of 0.3–0.7 s, which overlapped the period of natural oscillations of the examined building in the E–W direction. This additional low-frequency period of soil strata oscillations can be due to either a boundary in soil at a depth of 20–30 m that generates resonant vibrations or the incipient soil liquefaction effect. With the available data, we find it difficult to choose between these two plausible explanations. The above comparisons indicate the limitations of conducting seismic engineering surveys by microseism-analysis methods. Based on the analysis, recommendations are given on the orientation for this type of buildings under construction.